State officials are warning people to avoid contact with the water of Lake Hopatcong, New Jersey’s largest freshwater lake and popular tourist spot, because of green slime containing harmful organisms.

The state Department of Environmental Protection has received more than 30 reports of harmful algal bloom at the North Jersey lake since June 17, including incidents of mild skin rashes.

Exposure to HAB also may cause allergy-like reactions, flu-like symptoms, gastroenteritis, respiratory irritation and eye irritation.

HAB happens when cyanobacteria blooms produce a thick, bright green scum to appear on the surface of the lake. It can also appear as “spilled paint” or “pea soup.” This appearance is often taken for granted as a normal algae bloom.

The DEP says HAB could be a result of recent heavy rainfall carrying nutrient-rich stormwater into the lake, followed by spans of warm weather. The DEP began aerial surveillance of the lake last Wednesday and will continue to monitor the lake until it is safe.

That could take all summer.

The DEP also asked local health authorities to close the public beaches on the lake.

In 2017, the DEP released a campaign called “Avoid It and Report It”, which educates people about the blooms and how to properly report suspicious activity.

Their precautions are as follows:

  • Avoid contact with water in the vicinity of the bloom, especially in areas where the bloom is dense and forms scum;
  • Do not drink or consume the water;
  • Do not eat fish from the waterbody;
  • Keep pets and livestock away from the water;
  • Do not allow animals to drink the water, eat dried algae, or groom themselves after coming into contact with the water;
  • People, pets and livestock that come into contact with a bloom should rinse off with fresh water as soon as possible;
  • Seek medical attention or a veterinarian if a person or animal is experiencing adverse health effects after exposure to a bloom;
  • Report a suspected HAB by calling the DEP Hotline at 1-877-WARNDEP (877-927-6337) send a mobile alert through the WARN NJDEP mobile app (available via iTunes, Google Play or Windows Phone) or report via the DEP’s HAB website at